Chemical Equilibrium

If the forward reaction rate is equal to the rate of the reverse reaction, it is said that the system has reached a state of chemical equilibrium. It is said that a system is in a state of dynamic equilibrium when there is no further change in the concentrations of the reactants and products as a result of the equal rates of the forward and reverse reactions. Chemical Equilibrium is a state of equilibrium in a chemical reaction. Chemical Equilibrium is the state of being in equilibrium with one’s surroundings.

Dynamic Equilibrium

An equilibrium stage is defined as the point at which the rate of the forward reaction equals the rate of the backward reaction. It is at this point that the number of reactant molecules converting into products and the number of product molecules converting into reactants are equal. Chemical equilibrium is dynamic because it can be achieved with the same reactants anywhere in the world under similar conditions, and because molecules are constantly exchanging.

Categories of equilibrium 

1. Chemical Equilibrium in a Homogeneous Environment

In this type of chemical equilibrium, the reactants and products of chemical equilibrium are all in the same phase at the same time. It is possible to further classify homogeneous equilibrium into two types: A reaction where the number of molecules in the products equals the number of molecules in the reactants is known as a one-to-one match. As an illustration,

H2 (g) + I2 (g) → 2HI (g). 

N2 (g) + O2 (g) = 2NO (g)

Reactions in which the number of molecules produced by the products is less than the total number of molecules produced by the reactants. As an illustration,

2SO2 (g) + O2 (g) → 2SO3 (g) 

COCl2 (g) = CO (g) + Cl2 (g)

2. Chemical Equilibrium in a Heterogeneous Environment

In this type of chemical equilibrium, the reactants and products of chemical equilibrium are present in different phases of the reaction. A few examples of heterogeneous equilibrium are provided in the following section.

2CO = CO2 (g) + C (s) 

When CaCO3 (s) is combined with CO2, the result is CO2 (g)

Factors that influence equilibrium 

1. If there is any change in the factors affecting the equilibrium conditions, according to Le-law Chatelier’s of conservation of energy, the system will either counteract or reduce the effect of the overall transformation on the system. This principle holds true in both chemical and physical equilibrium situations.

2. There are a variety of factors that influence equilibrium, including the temperature, pressure, and concentration of the system. The following section discusses some of the most important factors that influence chemical equilibrium.

3. A change in concentration of the reactants or products added is caused by the reaction that consumes the substance that has been added a change in concentration of the reactants or products added.

4. The concentration of reactants or products removed is relieved by the reaction that is occurring in the direction that replenishes the substance that has been removed from the system.

5. When the concentration of a reactant or product is changed, the composition of the mixture in chemical equilibrium changes as a result of the change in concentration.

1. Change in Pressure:

When the volume of a fluid changes, the pressure of the fluid changes as well. Because the total number of gaseous reactants and products has changed as a result of the change in pressure, it is possible that the gaseous reaction will be affected. Following Le Chatelier’s principle, when a chemical equilibrium is achieved in heterogeneous conditions, the change of pressure can be ignored in both liquids and solids because volume is independent of pressure.

2. Change in Temperature: 

According to Le-Principle, Chatelier’s the effect of temperature on chemical equilibrium is dependent on the sign of the H of the reaction.

The equilibrium constant of an exothermic reaction decreases as the temperature of the reaction rises.

An endothermic reaction is one in which the equilibrium constant increases as the temperature of the reaction increases.

The rate of reaction is also affected by the change in temperature, in addition to the change in the equilibrium constant. According to Le Chatelier’s principle, when the temperature of an exothermic reaction rises, the equilibrium shifts towards the reactant side; however, when the temperature of an endothermic reaction rises, the equilibrium shifts towards the product side.

3. An effect of the catalyst: 

A catalyst has no effect on the chemical equilibrium of a reaction. It only serves to accelerate a reaction. In reality, a catalyst accelerates both the forward and the reverse reactions at the same rate. As a result, the reaction reaches equilibrium more quickly than it would otherwise.

Regardless of whether the reaction is catalysed or not, the same amount of reactants and products will be present at equilibrium in both cases. When a catalyst is present, the reaction can proceed more quickly through a lower-energy transition state of reactants to products, rather than stopping altogether.

4. The Effect of Adding an Inert Gas: 

When an inert gas such as argon is added to a constant volume of reaction mixture, it does not participate in the reaction and thus does not disturb the equilibrium. If the gas added is a reactant or product that is involved in the reaction, the reaction quotient will be altered accordingly.

Chemical Equilibrium Exemplifications

It is possible that products will be transformed back into reactive reactants in a chemical reaction. Reactive reactants will be converted into products in a chemical reaction by the forward reaction. The chemical compositions of the two states, reactants and products, are different.

It is possible that the rates of the forward and backward reactions will become equal after a period of time following the start of the reaction. Following this, the number of reactants converted will be formed again by the reverse reaction, resulting in the concentrations of reactants and products remaining unchanged for the remainder of the reaction. As a result, chemical equilibrium exists between the reactants and products.

Significant Impact of chemical equilibrium 

It is useful in a variety of industrial processes, including, for example,

It is possible to prepare ammonia using the Haber’s process. In this process, nitrogen reacts with hydrogen to form ammonia. The yield of ammonia is higher at low temperatures and high pressures, and when the process is carried out in the presence of iron as a catalyst.

Using the contacts process, sulphuric acid can be prepared: The fundamental reaction in this process is the oxidation of sulphur dioxide to form sulphur trioxide. Chemical equilibrium is required for this.

Conclusion 

Therefore, we can finally conclude from the whole article that chemical equilibrium occurs with the condition in the course of a reversible chemical reaction in which no net change in the amounts of reactants and products occurs. A reversible chemical reaction is one in which the products, as soon as they are formed, react to produce the original reactants.